Evidence of spatial clustering of childhood acute lymphoblastic leukemia cases in Greater Mexico City: report from the Mexican Inter-Institutional Group for the identification of the causes of childhood leukemia

Background

A heterogeneous geographic distribution of childhood acute lymphoblastic leukemia (ALL) cases has been described, possibly, related to the presence of different environmental factors. The aim of the present study was to explore the geographical distribution of childhood ALL cases in Greater Mexico City (GMC).

Methods

A population-based case-control study was conducted. Children <18 years old, newly diagnosed with ALL and residents of GMC were included. Controls were patients without leukemia recruited from second-level public hospitals, frequency-matched by sex, age, and health institution with the cases. The residence address where the patients lived during the last year before diagnosis (cases) or the interview (controls) was used for geolocation. Kulldorff's spatial scan statistic was used to detect spatial clusters (SCs). Relative risks (RR), associated p-value and number of cases included for each cluster were obtained.

Results

A total of 1054 cases with ALL were analyzed. Of these, 408 (38.7%) were distributed across eight SCs detected. A relative risk of 1.61 (p<0.0001) was observed for the main cluster. Similar results were noted for the remaining seven ones. Additionally, a proximity between SCs, electrical installations and petrochemical facilities was observed.

Conclusions

The identification of SCs in certain regions of GMC suggest the possible role of environmental factors in the etiology of childhood ALL.

Precision Oncology in Pancreatic Cancer. From Surgery- to Genetic-Based Chemotherapy

Pancreatic ductal adenocarcinoma is one of the most lethal forms of solid tumors. These tumors arise from the exocrine component of the pancreas, probably from acinar stem cells1-3.

R-Spondin-2 Is Upregulated in Idiopathic Pulmonary Fibrosis and Affects Fibroblast Behavior

Idiopathic pulmonary fibrosis (IPF) is characterized by the expansion of the myofibroblast population, excessive extracellular matrix accumulation, and destruction of the lung parenchyma. The R-spondin family (RSPO) comprises a group of proteins essential for development. Among them, RSPO2 is expressed primarily in the lungs, and its mutations cause severe defects in the respiratory tract. Interestingly, RSPO2 participates in the canonical Wingless/int1 pathway, a critical route in the pathogenesis of IPF. Thus, the aim of this study was to examine the expression and putative role of RSPO2 in this disease. We found that RSPO2 and its receptor leucine-rich G protein-coupled receptor 6 were upregulated in IPF lungs, where they localized primarily in fibroblasts and epithelial cells. Stimulation of IPF and normal lung fibroblasts with recombinant human RSPO2 resulted in the deregulation of numerous genes, although the transcriptional response was essentially distinct. In IPF fibroblasts, RSPO2 stimulation induced the up- or downregulation of several genes involved in the Wingless/int1 pathway (mainly from noncanonical signaling). In both normal and IPF fibroblasts, RSPO2 modifies the expression of genes implicated in several pathways, including the cell cycle and apoptosis. In accordance with gene expression, the stimulation of normal and IPF fibroblasts with RSPO2 significantly reduced cell proliferation and induced cell death. RSPO2 also inhibited collagen production and increased the expression of matrix metalloproteinase 1. Silencing RSPO2 with shRNA induced the opposite effects. Our findings demonstrate, for the first time to our knowledge, that RSPO2 is upregulated in IPF, where it appears to have an antifibrotic role.

Is there something else besides the proapoptotic AVPI-segment in the Smac/DIABLO protein?

In mammals, apoptosis is the main mechanism to eliminate unwanted cells, securing tissue homeostasis and consequently maintaining the health in the organism. Classically, apoptosis culminates with the activation of caspases, which are enzymes that display cysteine protease activity to degrade specific substrates implied in essential cellular processes. This process is highly regulated. A key regulation mechanism is mediated by the Inhibitor of Apoptosis Proteins (IAPs) family members, which inhibit the activated forms of caspases through physical interaction with them. Smac/DIABLO, a mitochondrial protein that is translocated to the cytoplasm in apoptotic conditions, derepresses the IAP-mediated caspase inhibition through physical interaction with IAPs. The first four amino acids (AVPI) of Smac/DIABLO mediate the interaction with IAPs and subsequent apoptosis induction. This interaction has lead to the creation of small molecules mimicking the AVPI segment for potential anticancer therapy. Nevertheless, several studies have pointed out the existence of AVPI-independent functions of Smac/DIABLO. The aim of this review was to provide a landscape of these underestimated AVPI-independent biological functions that have been observed using different approaches, such as the study of endogenous splice variant isoforms and truncated and mutated artificial proteins.

Induction of c-Jun by air particulate matter (PM₁₀) of Mexico city: Participation of polycyclic aromatic hydrocarbons

The carcinogenic potential of urban particulate matter (PM) has been partly attributed to polycyclic aromatic hydrocarbons (PAHs) content, which activates the aryl hydrocarbon receptor (AhR). Here we report the effect of PM with an aerodynamic size of 10 μm (PM10) on the induction of AhR pathway in A549 cells, evaluating its downstream targets CYP1B1, IL-6, IL-8 and c-Jun. Significant increases in CYP1B1 protein and enzyme activity; IL-6 and IL-8 secretion and c-Jun protein were found in response to PM10. The formation of PAH-DNA adducts was also detected. The involvement of AhR pathway was confirmed with Resveratrol as AhR antagonist, which reversed CYP1B1 and c-Jun induction. Nevertheless, in IL-6 and IL-8 secretion, the Resveratrol was ineffective, suggesting an effect independent of this pathway. Considering the role of c-Jun in oncogenesis, its induction by PM may be contributing to its carcinogenic potential through induction of AhR pathway by PAHs present in PM10.

[Cancer genomes: where do we go from here?]

In recent years there has been an exponential growth of knowledge of the molecular basis of cancer. In particular, the creation of important initiatives for the elucidation of the genomes of several types of cancer has allowed for the first time the creation of catalogs for most mutational events in diverse tumors, which opens up significant opportunities for oncology and public health. This review provides an overview of the progress and possible directions in Mexico.

Increased expression of prostaglandin reductase 1 in hepatocellular carcinomas from clinical cases and experimental tumors in rats

To identify novel tumor-associated proteins, we analyzed the protein expression patterns from experimental hepatocellular carcinoma (HCC) that were induced using hepatocarcinogenesis models in rats. Rats were subjected to two previously described protocols of hepatocarcinogenesis using diethylnitrosamine as a carcinogen: the alternative Solt-Farber (aS&F) protocol, which induces HCC within 9 months, and Schiffer's model, which induces cirrhosis and multifocal HCC within 18 weeks. The patterns of protein expression from tumors and normal liver tissue were examined by SDS-PAGE and the bands identified at 33-34 kDa were analyzed by mass spectrometry. The prostaglandin reductase 1 (PTGR1) showed the highest number of peptides, with a confidence of level >99%. The increased expression of PTGR1 in tumors was confirmed in these two models by Western blotting and by increase in alkenal/one oxidoreductase activity (25-fold higher than normal liver). In addition, the gene expression level of Ptgr1, as measured by qRT-PCR, was increased during cancer development in a time-dependent manner (200-fold higher than normal liver). Furthermore, PTGR1 was detected in the cytoplasm of neoplastic cells in rat tumors and in 12 human HCC cases by immunohistochemistry. These analyses were performed by comparing the expression of PTGR1 to that of two well-known markers of hepatocarcinoma, Glutathione S-transferase pi 1 (GSTP1) in rats and glypican-3 in humans. The increased expression and activity of PTGR1 in liver carcinogenesis encourage further research aimed at understanding the metabolic role of PTGR1 in HCC and its potential application for human cancer diagnosis and treatment.

Abstract PL07-01: Molecular profiling of breast cancer in Mexico: Identification of novel therapeutic targets through whole genome sequencing analysis

Today, more than 55% of the world's breast cancer cases are diagnosed in low and middle-income countries and in 2020, more that 70% of the cases will come from the developing nations. In Mexico, breast cancer-specific mortality doubled during the past 20 years, representing the second-leading cause of death in women between 30 and 59 years and the leading cause of cancer related death in the female population. According to statistics, in Mexico a woman dies due to breast cancer every two hours. Even though breast cancer represents a major public health problem in the developing world, knowledge about the genetic and genomic structure of breast tumors in Mexican or Latin American populations is very limited. In the past four years, we have participated in the Slim Initiative of Genomic Medicine (SIGMA) Project, a collaboration between the Carlos Slim Institute of Health, the Broad Institute, and the National Institute of Genomic Medicine in Mexico city. The goal of the SIGMA project is to characterize the genomic basis of common diseases, including several types of cancer. This effort has focused on the application of whole genome and whole exome sequencing of human tumors. In the case of breast cancer, we have analyzed the whole genomes of 22 tumor/normal tissue pairs and the whole exomes of 103 tumor/normal tissues from Mexican and Vietnamese patients. Sequence analysis led to the novel identification of potential loss of function mutations of the CBFB transcription factor, and deletions of its partner RUNX1, an event which has never been previously reported in breast tumors or in any other epithelial tumor. Of clinical relevance, we also identified a somatic translocation involving MAGI3 and AKT3 in a triple negative breast tumor. Ectopic expression of the fusion transcrip leads to constitutive phosphorylation of downstream GSK and loss of contact inhibition. Most importantly, the activity of the fusion protein can be abrogated by an ATP-competitive small molecule inhibitor of AKT, potentially representing a new therapeutic avenue for these patients. In parallel with sequencing, we have also been working on the analysis of somatic DNA copy number aberrations, messenger RNA expression, and microRNA expression patterns in tumors from Mexican patients. Intrinsic breast cancer sub-typing in 125 tumors from Mexican patients showed that 13.6% of the tumors were basal-like, 16.8% were Her2-enriched, 24.8% Luminal A, 34.4% Luminal B and 10.4 normal-like. With microRNA expression, we have identified a group of microRNAs whose role in breast cancer has not been previously described and are currently analyzing differential microRNA expression across tumor sub-types, in particular triple negative tumors, where we have been able to identify at least three different tumor sub-groups based on microRNA expression patterns.

Citation Format: Shantanu Banerji, Kristian Cibulskis, Claudia Rangel-Escareño, Kristin K. Brown, Scott L. Carter, Abbie M. Frederick, Michael S. Lawrence, Andrey Y. Sivachenko, Carrie Sougnez, Lihua Zou, Maria L. Cortes, Juan C. Fernandez-Lopez, Shouyong Peng, Kristin G. Ardlie, Daniel Auclair, Veronica Bautista-Piña, Fujiko Duke, Joshua Francis, Joonil Jung, Antonio Maffuz-Aziz, Robert C. Onofrio, Melissa Parkin, Nam H. Pho, Valeria Quintanar-Jurado, Alex H. Ramos, Rosa Rebollar-Vega, Sergio A. Rodríguez-Cuevas, Sandra L. Romero-Cordoba, Steven E. Schumacher, Nicolas Stransky, Kristin M. Thompson, Laura Uribe-Figueroa, Jose Baselga, Rameen Beroukhim, Kornelia Polyak, Dennis C. Sgroi, Andrea L. Richardson, Gerardo Jimenez-Sánchez, Eric S. Lander, Stacey B. Gabriel, Levi A. Garraway, Todd R. Golub, Jorge Meléndez-Zajgla, Alex Toker, Gad Getz, Matthew Meyerson, Alfredo Hidalgo-Miranda. Molecular profiling of breast cancer in Mexico: Identification of novel therapeutic targets through whole genome sequencing analysis. [abstract]. In: Proceedings of the Fifth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2012 Oct 27-30; San Diego, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2012;21(10 Suppl):Abstract nr PL07-01.

Cancer stem cells

There are two hypotheses that explain tumor progression. The first one, the stochastic hypothesis, assumes that any cell within a tumor has the capacity to form and maintain the tumor mass. The second, the so-called hierarchical hypothesis, suggests the existence of a group of cells with a stem phenotype which, like in normal tissues, preserves tumors through a continuous production of progeny. These stem cells are in a particular niche, have a higher resistance to chemotherapy and radiotherapy, and are also capable of invading and migrating to other tissues. This review describes the cancer stem cells (CSCs), their function inside a tumor and the current knowledge about these cells.

Renoprotection by alpha-Mangostin is related to the attenuation in renal oxidative/nitrosative stress induced by cisplatin nephrotoxicity

Cisplatin (CDDP) is a chemotherapeutic agent that produces nephrotoxicity associated with oxidative/nitrosative stress. alpha-Mangostin (alpha-M) is a xanthone extracted from mangosteen with antioxidant and anti-inflammatory properties. The purpose of this study was to evaluate the renoprotective effect of alpha-M on the CDDP-induced nephrotoxicity. alpha-M was administered (12.5 mg/kg/day, i.g.) for 10 days (7 days before and 3 days after CDDP injection). On day 7, rats were treated with a single injection of CDDP (7.5 mg/Kg, i.p.); 3 days after the rats were killed. alpha-M attenuated renal dysfunction, structural damage, oxidative/nitrosative stress, decrease in catalase expression and increase in mRNA levels of tumour necrosis factor alpha and transforming growth factor beta. In conclusion the renoprotective effect of alpha-M on CDDP-induced nephrotoxicity was associated with the attenuation in oxidative/nitrosative stress and inflammatory and fibrotic markers and preservation of catalase activity.

[Is cancer a transmittable disease?]

A direct, horizontal and natural transmission of neoplasic cells has only recently been accepted by the biomedical community. There are three known examples in mammals: the Tasmanian Devil Tumor Disease, the Canine Transmissible Venereal Tumor and a similar disease in Sirian Hamsters. These diseases are not anecdotic cases only, but provide support for the cancer clonal evolution hypothesis.

External membrane vesicles from Helicobacter pylori induce apoptosis in gastric epithelial cells

The Helicobacter pylori infection of gastric mucosa is one of the most common infectious diseases and is associated with a variety of clinical outcomes, including peptic ulcer disease and gastric cancer. Helicobacter pylori-induced damage to gastric mucosal cells is controlled by bacterial virulence factors, which include VacA and CagA. Outer membrane vesicles are constantly shed by the bacteria and can provide an additional mechanism for pathogenicity by releasing non-secretable factors which can then interact with epithelial cells. The present report shows that external membrane vesicles are able to induce apoptosis not mediated by mitochondrial pathway in gastric (AGS) epithelial cells, as demonstrated by the lack of cytochrome c release with an activation of caspase 8 and 3. Apoptosis induced by these vesicles does not require a classic VacA+ phenotype, as a negative strain with a truncated and therefore non-secretable form of this protein can also induce cell death. These results should be taken into account in future studies of H. pylori pathogenicity in strains apparently VacA-.

Tumor HGF lacks prognostic significance in Mexican breast cancer patients

Hepatocyte growth factor-scatter factor (HGF-SF) is a pleiotropic protein implicated in tumor formation and metastasis. Since increased levels of HGF-SF were first identified in breast cancer tissue or patient serum, some evidence has suggested that tumor or serum HGF-SF concentration could be one of the most accurate prognostic factors for this disease. However, other recent investigations have not been able to corroborate this finding. The study aims to establish the prognostic significance of HGF-SF in Mexican breast cancer women. Surgical specimens were obtained from 67 incident breast cancer patients at the Mexican National Cancer Institute between 1994 and 1995. Primary breast cancer tissue HGF-SF was measured by quantitative sandwich enzyme immunoassay. Relapse-free and overall survival curves were generated using Kaplan-Meier method. Significance of survival differences was calculated by log-rank test. chi2 was used for the association analysis between prognostic variables. Disease-free survival and overall survival were similar between the high tumor HGF group of patients and the low HGF patients (p = 0.7 and p = 0.36 respectively). No association was found between HGF and other clinicopathological variables (age, menopause status, clinical tumor size, clinical node involvement, metastasis, tumor grade, Estrogen Receptor and Progesterone Receptor). We found no prognostic significance for HGF, nor did we find a clear association between HGF and other known prognostic factors. A firm conclusion cannot be established regarding the role of HGF as a prognostic tool in breast cancer patients.

Benzene metabolites induce apoptosis in lymphocytes

Benzene is an important environmental pollutant with important health implications. Exposure to this aromatic hydrocarbon is associated with hematotoxicity, and bone marrow carcinogenic effects. It has been shown that benzene induces oxidative stress, cell cycle alterations, and programmed cell death in cultured cells. Hepatic metabolism of benzene is thought to be a prerequisite for its bone marrow toxicity. Nevertheless, there are no reports on the cellular effects of reactive intermediates derived from hepatic metabolism of benzene. Thus, the goal of this project was to determine the cellular alterations of benzene metabolites produced by the cultured hepatic cell line HepG2. Supernatants collected from these cells were applied to a culture of freshly isolated lymphocytes. A higher decrease in cell viability was found in cells exposed to these supernatants than to unmetabolized benzene. This viability decrease was due to apoptosis, as determined by Terminal deoxynucleotidyl Transferase Biotin-dUTP Nick End Labeling (TUNEL) assay and internucleosomal fragmentation of DNA. When supernatants were analyzed by HPLC, we found that not all the hydrocarbon was biotransformed, since a 28 microM concentration (37%) remained. The only metabolite found in the culture medium was muconic acid. The present results show that muconic acid derived from benzene metabolism is able to cooperate with the pollutant for the induction of apoptosis in rat lymphocytes.

Tissue inhibitor of metalloproteinases-2 growth-stimulatory activity is mediated by nuclear factor-kappa B in A549 lung epithelial cells

Tissue inhibitors of metalloproteinases (TIMPs) are pleiotropic factors that function as key regulators of extracellular matrix remodeling. They exhibit multifunctional roles including cell growth-stimulating activities and protection from apoptosis. In the present study, we showed that human recombinant TIMP-2 (hrTIMP-2) promotes growth of A549 lung cells. This effect was accompanied by increase in nuclear factor-kappa B (NF-kappaB) activity 24h after exposure as determined by electrophoretic mobility shift assay (EMSA) analysis. This effect was correlated with downregulation of IkappaBalpha and beta proteins and later increases in Bcl-3, IkappaB, and cyclin D1 proteins. Blocking induction of NF-kappaB activity using a dominant-negative mutated version of IkappaBalpha abrogated NF-kappaB activation and cell proliferation.

Oxaliplatin activity in head and neck cancer cell lines

Oxaliplatin (cis-[(1R,2R)-1,2-cyclohexanediamine-N,N'] [oxalato(2-)-O,O'] platinum; Eloxatin) is a third-generation platinum compound with a 1,2-diaminocyclohexane (DACH) carrier ligand, which has a wide spectrum of anticancer activity in vitro systems and has displayed preclinical and clinical activity in a wide variety of tumors. To investigate its in vitro activity against head and neck cancer, we exposed two head and neck cancer cell lines to the compound, created a variant resistant to cisplatin to study cross-resistance to the compound and analyzed the potential radiosensitizing effect of the drug. We report here that oxaliplatin was cytotoxic at similar doses to cisplatin in these cells. There was no cross-resistance to cisplatin, as demonstrated by different IC50 values in these cell lines and the sensitivity to oxaliplatin of the cisplatin-resistant cell line. There was an effective radiosensitizer effect of the compound in either cell line. Additional in vitro and in vivo experimentation is warranted in order to support the use of oxaliplatin as a radiosensitizer in head and neck cancer patients.

Cytogenetic analysis of the mononuclear cell component of giant cell tumors of bone

This study comprises the cytogenetic analysis of mononuclear cells of a Mexican patient with a giant cell tumor of bone. This cell line showed nine translocations, two duplications, one addition, one deletion, and one ring chromosome, and did not present telomeric association.

[Caspases: apoptosis inducing molecules]

Caspases are key proteins for the transduction and ejection of the apoptotic signals induced by several stimuli. These proteins are present within the cell as inactive precursors that need a proteolytic cleavage in order to be active. There are two main caspases group, the initiators and executors. The formers are activated by autoproteolysis when translocated to specific cell compartments or trough the coupling of adapters and or activators. The executors caspases are activated by cleavage of an initiator caspase. These proteases are responsible then for the final cleavage of diverse substrates that mediate the morphologic changes during apoptosis. Among these there are signalization, DNA repairing, structure, transcription proteins, etc. Caspases represent a new paradigm in the signal transduction pathway, and are implicated in a large number of physiologic and pathologic processes. In a near future they could be useful pathologic markers and therapeutic targets.

Cupressus lusitanica (Cupressaceae) leaf extract induces apoptosis in cancer cells

A crude ethanolic extract of Cupressus lusitanica Mill. leaves demonstrate cytotoxicity in a panel of cancer cell lines. Cell death was due to apoptosis, as assessed by morphologic features (chromatin condensation and apoptotic bodies formation) and specific DNA fragmentation detected by in situ end-labeling of DNA breaks (TUNEL). The apoptotic cell death was induced timely in a dose-dependent manner. Despite the absence of changes in the expression levels of antiapoptotic protein Bcl-2, proapoptotic Bax protein variants omega and delta were increased. These results warrant further research of possible antitumor compounds in this plant.

Gemcitabine activity in cervical cancer cell lines

PURPOSE

Gemcitabine (2',2'-difluorodeoxycytidine) is an antineoplastic agent with activity against a variety of solid tumors. To investigate its in vitro activity toward cervical cancer, we exposed six cervical cancer cell lines to gemcitabine.

METHODS

Combinational cytotoxic studies using viability tests and clonogenicity assays.

RESULTS

Gemcitabine was cytostatic and cytotoxic in some of the lines at peak plasma concentrations similar to those achieved in clinical trials. Gemcitabine was also found to effectively synergize with cisplatin and showed a radiosensitizing effect in these cells. The cytotoxicity observed in sensitive cell lines was due to apoptosis, as demonstrated by DNA fragmentation assays.

CONCLUSIONS

We recommend performing additional in vitro experimentation so that these results can be confirmed to support clinical trials of gemcitabine in cervical cancer patients both as first-line therapy and with concomitant radiation.

Inhibitor of apoptosis-1 (IAP-1) expression and apoptosis in non-small-cell lung cancer cells exposed to gemcitabine11Abbreviations: IAP, inhibitor of apoptosis; TNF-α, tumor necrosis factor-α; NF-κB, nuclear factor-κB; RT-PCR, reverse transcriptase-polymerase chain reaction; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; and DTT, dithiothreitol

Exposure of lung cancer cells to gemcitabine (2',2'-difluorodeoxycytidine) arrests cells in S phase and induces secondary apoptotic cell death. Gemcitabine treatment decreased the expression of IkappaB-alpha protein and, concomitantly, increased the activity of nuclear factor-kappaB (NF-kappaB) transcription factor, a known inhibitor of the apoptotic response. This increase was accompanied by a similar increment in the expression of inhibitor of apoptosis-1 (IAP-1) protein and mRNA, a caspase inhibitor responsive to NF-kappaB. These changes were important to the final destiny of the cells, since overexpression of a dominant negative version of IkappaB-alpha, which suppresses NF-kappaB activation, blocks the increase of IAP-1 protein and potentiates the action of gemcitabine. Additionally, overexpression of IAP-1 protein in A549 cells expressing the IkappaB-alpha mutant restored the initial sensitivity to gemcitabine and demonstrated that this protein was responsible for the inhibitory effect of NF-kappaB. These results support the notion of IAP-1 as an important antiapoptotic protein mediating sensitivity to deoxynucleotides analogs in non-small-cell lung cancer cells.

Modulation of NF-kappa B, and Bcl-2 in apoptosis induced by cisplatin in HeLa cells

Cisplatin exposure induces apoptosis in HeLa cells. Since the interaction of this drug with DNA produces reactive oxygen species, we performed an analysis of the oxidative stress-responsive factors AP-1 and NF-kappa B. Although AP-1 levels were not modified during cisplatin exposure, electrophoretic mobility shift assays demonstrated an increase in NF-kappa B DNA binding activity that correlated with a decrease of the inhibitory protein I kappa B alpha and a specific relocalization of c-Rel, as assessed by immunoblotting and immunofluorescence. No changes in the levels or localization of p65 were found. Interestingly, I kappa B alpha relocalized to the nucleus, probably in order to regulate the binding of specific complexes. This process was accompanied by a decrease of the antiapoptotic protein Bcl-2, and a relocalization of p53 protein to the nucleus. Since HeLa cells lost most of their p53 protein due to a specific E6-dependent degradation, cisplatin could be inhibiting this degradation, since the p53 total levels were not increased during the exposure to the drug.

Subcellular redistribution of HSP72 protein during cisplatin-induced apoptosis in HeLa cells

Exposure of HeLa cells to cisplatin results in the activation of apoptotic cell death. This drug induces DNA damage and generates reactive oxygen intermediates. Since cisplatin is highly reactive and binds to diverse proteins, it could create abnormal protein structures or nonspecific aggregates. For these reasons, we analyzed the expression and subcelullar distribution of hsp72, a heat-shock protein that enables cells under stress to cope with damaged proteins. We did not observe any changes in the expression of hsp72 protein, although, by immunofluorescence studies, we detected a dramatic redistribution of the protein. These results and its probable relevance in the drug-induced apoptotic phenomenon are discussed.

Paclitaxel-induced apoptosis in HeLa cells is serum dependent

Exposure of HeLa cells to different concentrations of the antineoplastic drug paclitaxel resulted in a loss of cell viability that was dependent on the concentration and time of exposure to the drug. This phenomenon was associated with the appearance of nuclear morphology typical of apoptosis and DNA breakage into a "ladder" pattern of discrete fragments of nucleosomal size. The induction of cell death was dependent on the serum concentration of the culture media, repressed by pretreatment with a cAMP-dependent protein kinase (PKA) inhibitor, and enhanced by increasing the cell proliferation with previous exposure to a cAMP-analog and a protein kinase-C (PKC) inducer. The proliferative index modifies the effect of taxol on HeLa cells, probably by means of a more rapid accumulation of cells in the G2/M cycle blockage point, although a direct participation of PKA and PKC should not be excluded.